Mastering Ethereum

Appendix A. Ethereum Fork History

Most hard forks are planned as part of an upgrade roadmap and consist of updates that the community generally agrees to (i.e., there is social consensus). However, some hard forks lack consensus, which leads to multiple distinct blockchains. The events that led to the Ethereum/Ethereum Classic split are one such case, and are discussed in this appendix.

Ethereum Classic (ETC)

Ethereum Classic came to be after members of the Ethereum community implemented a time-sensitive hard fork (codenamed “DAO”). On July 20, 2016, at a block height of 1.92 million, Ethereum introduced an irregular state change via a hard fork in an effort to return approximately 3.6 million ether that had been taken from a smart contract known as The DAO. Almost everyone agreed that the ether taken had been stolen and that leaving it all in the hands of the thief would be of significant detriment to the development of the Ethereum ecosystem as well as the platform itself.

Returning the ether to its respective owners as though The DAO had never even existed was technically easy, if rather politically controversial. A number of people in the ecosystem disagreed with this change, believing immutability should be a fundamental principle of the Ethereum blockchain without exception; they elected to continue the original chain under the moniker of Ethereum Classic. While the split itself was initially ideological, the two chains have since evolved into separate entities.

The Decentralized ...